Production of leather



Patented Junell, 1935 I r I v PRODUCTION OF LEATHER George. R. 'Pensel, Amsterdam, N, Y. I N"Drajwlng. Application April 21, 1933, Serial No. 667,306 f l s 2 Claims, (01.149-3) V I This invention relates to the-"production of is applied directly't'othe skinsas received and leather from hides orskins, and morepa'rticularly prior to the actual tannag'e. One exceptionto totanning processes'inwhich'the-hides or skins this procedure may occur in cases in which the are subjected to certain novel treatin'entpriorl to skins are degreased. This preliminarytreatment 5 the actual tanning thereof. i I comprises what might be termed a re-pickling?! 5 hisI preliminary treatnient has special applistep or, in other words, a substitution process by cation to chrome tanning, although it may be used which-the strong acid jplckle is replaced by a to great advantage in other-types of tanning weaker acid, preferablyotj an organic nature, l processes, including" those in. which formaldehyde and whereby the pH number is raised from about in or other aldehydes farejemployediinvegetable 2.0 to the neighborhood of 5.0. This re- 10 tanning processes or the so-called bark tannages, picking has been found beneficial in all types and also inoil tannages. of tanning whetheraldehyde, bark orchrome,

The present application is a continuation in but more especially in the last named type in part of my prior application 'Ser. Nels-11,122, connection with whichmost remarkable results filed May 29,1931, and has for its general object have been obtained. I Formerly, successful 15 the provision of noveland improved methods and chrometannage processes involvedjsoaking "the compositions foreffectingth'e tanning processes skins in the tan liquorallday with constant to which reference hasbeen made. additions-of materialend supervision; and'the As is generally wellknown, before being tanned most rapidphrome tanning previously attained or converted into leather, hides and skins are has taken fromfive tote'nhours. But it has been 20 subjected "to certain preliminary processes infound that by pursuing the process involving the ;cluding the steps of dehairing, limingbatingand principles of thepresent'invention the skins may beaming. Uponremovalfrom the beamhouse, be chrome tanned so as tofstand the iamiliar the skins are placed in a picklinglbath which boiling test in about fifteen minutes. So-called "almost invariably" comprises asolution 0i sul-'- short tanning processes to which reference has 25 phuric acid and common salt. Although pickling "beenmade, were dependent upon high concensolutions are usedfor-numerous reasonsjthechief trations of basic chromium sulphate solutions purpose oi. the pickling process is to preserve the and neutralization with alkalies. Thechromium unhaired skins so that they maybe kept for an in my method flxedwithout the use of alkaindefinite'period before tanning; as for example, lies, j l I I in the case of skins obtained from abroad. Such The complete-theory and explanation of the skins are received in a semi-wet state due to the present invention is not thoroughly understood adhering pickling solution, sothat, for example; a in all its details; but it is well recognized that dozen skins of a certain kind and size that weigh the fundamental operations in the complete approximately twenty "or twenty-one pounds in tannage processare interdependent, and therei the pickle, weigh only about eight poundswhen iorethis invention comprises not only the novel dry. These pickled skins are quite strongly acid preliminary acid substitution or re-pickling and generally have'a. pH value of from 1.9 to 2.2. but the novel combination of this'treatment with I In previous vegetable tanning processes, these the subsequent tanning process. 1

40 strongly acid skins have been subjected to. a neu- In its preferred embodiment, my new method tralizing or depickling process by the use of an may be briefly describedas involving the subalkali such asborax orsodium bicarbonate so as stituti'on of acetic or other relatively weak orvtobring the hydrogen ion concentration of the jganicl acid for the sulphuric acid in the pickled skins to about pH3 or 4. In the case of aldehyde skin's, whereby among. other eflects', the pH numtannage the range of pH valuesprior. to tanning 'berofthe'batch israised'to the neighborhood .0!

have run from 'Ito 12, but the pH numbers have 4.8-610 controlling the temperatures and congenerally been brought down to the neighborhood centration off the various salts, acids and bases of 7 to 9 during the actual aldehyde tanning steps. involved within certain limits to better etfectw- It is noteworthy that in prior processesof chrome ate the process; and then tanning the skins by tanning, it has not been considered necessary to certain rapid but eilfectivesteps to be described depiclcle the skins. V i V indetail in the specification to follow. In the My novel and particularly effective preliminary chrome tannage to which the present invention treatment is applied to the :skins after. the is most particularly adaptable; the pH numbers pickling step. Generally in the case of importof the 'tannagebaths are also. maintained. at

ed skins which are pickled abroad, the treatment 'values in the neighborhood of 5.0. In the case 5 of the formaldehyde tannage the pH number of the bath after depickling may be as high as 5.5, and during early tanning stages about 7.4, where it is maintained as closely as possible by the addition of suitable agents.

In order to present a complete disclosure whereby the invention may be practiced by one skilled in the art, the following detailed descriptions are submitted merely by way of example, the invention not being limited to the detailed steps and quantities named except within the scope of the subjoined claims.

A formaldehyde tannage has been successfully effected as follows: 468 pounds of skins (pickled weight) were fioatedin a revolving drum in about 100 gallons of the following solution: About 150 pounds of Glaubers salt (for suede leather about 100 pounds and for strong grain leather about 200 pounds); 44 pounds of sodium acetate (9 of the pickled weight of the skins); 6.1 pounds of 84% acetic acid (1.3% pickled weight of skins). The drum containing the skins and this solution wasrevolved for. about 30 minutes at. about The. pH number of the bathwasat that time about 5.1. 7

The solution thus prepared was added to the drumand the latter was revolved for about 30 minutes. The pH number was then in'the neighborhood of 5.5. V

The skins were then slatted off, or, in other words, drained in a rotating drum having a door with open slots or holes through which most of the liquor in the skins may drain away, and they were ready for the actual tanning process. One hundred gallons of the tanning solution were prepared as follows: 150 pounds Glaubers salt; 20 pounds borax (about 4% of the pickled weight of the skins) 58 pounds (about 12%) of Paratan or formaldehyde tanning 7 compound; about 1.2 pounds of 84% acetic acid (0.25% of pickled weight of skins). The drum containing the pickled skins was revolved and this tanning solution was added at a final temperature of 80 F. The drum was revolved for one hour and the pH number was then found to be about 7.4, and the temperature of the bath is raised to about F. There was added about 14 pounds (3%) of a suitable sulphonated oil, the drum was revolved for 10 minutes and the temperature raised to about F. Enough borax was added along with the sulphonated oil to insure that there would be no change in the pH number. vThe drum was then revolved for about 30 minutes at 120 F.; the temperature was raised to F. during another 30 minute run; the bathwas then run for 30 minutes to F., and was then run for another 30 minute period at 140 F. The pH number was still about 7.4. The skins were then washed until they were reduced to a temperature of about 80 F.

It is to be noted that the amount of borax added epends to'some extent on the acidity of the original pickle and upon the pH value, in the neighborhood of 7, desired. For s'o-called doeskins or suede leather, it is necessary to tan at a pH number slightly below 'lin order to keep the skins firm 'or slightly under-tanned, while in the case of grain leather, it is necessary to tan at a pH value of. above 7 in order to obtain a strong grain.

, Specific examples of the chrome tannage proccss are as follows:

I. About 450 pounds of skins containing their absorbed strong acid pickling at about pH 2.1

were run in a revolving drum for about 30 min utes at 90 F. in 100 gallons of a float containing about pounds Glaubers salt at 80 F.; 40.5 pounds sodium acetate (approximately 9% of the pickled weight of the skins); 5.85 pounds acetic acid (1.3% of pickled weight of skins) and water. The pH value of the skins was then about 5.1.

There was then added to the drum 9.0 pounds of borax (approximately 2%) in 25 gallons of water together with enough Glaubers salt to obtain a salt concentration of about 15% (about 150 pounds) the drum was then revolved for about 30 minutes and the pH value was found to still be in the neighborhood of 5.1. The skins were slatted off and were subjected to a chrome tannage as follows:

About 100 gallons of an aqueous solution containing about 84 pounds (10% concentration) of Glaubers salt crystals or 48 pounds (about 6%) of common salt was introduced, the drum was started, and there was added in three feeds about five minutes apart, a 30% (3 pounds per gallon) aqueous solution of basic chromium sulphate. At the end of 15 minutes the chrome solution was practically exhausted and the skins were sufficiently tanned to stand a boil. The pH number after the tanning was about 4.8-5.0.

Finally, the skins are neutralized with a 1% b orax solution to a pH number of 5.9 for coat 4 leather and 6.2 for glove leather, using in the latter case 2% borax based on the pickled weight of skins. It is only necessary then to go ahead with the usual process of fat liquoring or re-tanhing for special leathers. In order to produce tighter or looser leather, the pH number may be altered slightly in the depickling stages by the use of sodium formate, sodium acetate, sodium lactate, or other salts of organic acids. 1

II. The following is an example of a chrome tanning process as applied to certain domestic skins. Approximately 450 pounds of pickled skins had a pH number of 1.2. The heat was prepared by dissolving 63pounds common salt (about 13.8% of the pickled weight of the skins), 42 pounds of a neutralizer, preferably-sodium acetate (about 9%), and about 5 pounds of 84% acetic acid (about 1.2%). The skins were run in this float for about 20 minutes and the pH value was determined to be approximately 4.9. Then about 9 pounds 6 ounces of borax (2% of pickled weight) and about 40 pounds of common salt were added to the float and the drum was run for about 20 minutes, whereupon the pH number was found to be 4.9-5.0. The skins were then drained for 40 minutes.

In the actual tanning stage, a solution is prepared by adding 37 pounds of basic chromium sulphate of a basicity of 38 (8% pickled weight) to 12 gallons of water and an equal quantity of common. salt in about lii gallons of water at 80F. This tanning solution was added to the skins in three feeds, five minutes apart and the run was continued for 10minutes after the last 'feed (total tanning time 25 minutes). The pH number of the skins was then at about 4.9-5.0.

Certain of the skins were then removed for suede finishing and others for fieshing. The fleshed skins were then returned to the drum in the amount of 233 pounds. They were washed with water at 80 F. for 15 minutes and heated to 110 F. There was then added 2 pounds 5 ounces of borax (1% weight of skins). in three feeds, five minutes apart, at 110 F. The pH number was found to be 5.1.

The skins werewashed for l5jminutes at 110 F. and then about 9 pounds (4%) of a synthetic tannin in 6 gallons of water at 110 F. was added" and the drum was rotated for 20 minutes. The pH value was then about 5.0'. This synthetic tannin is made from orthocresol, ,sulphonated and condensed with formaldehyde; the sulphonic acid being partially neutralized and buffersbeing used to raise the pH number; The skins. were-then washed for 15 minutes at 120 F. andthe temperature was then raised to 130 F. They were then put through a fat-liquoring' process with suitable compounds, such as sulphonated sperm and,

It may be noted atthis pointthat instead of using either Glauberssalt or common salt along with the borax in the neutralizing step following the initial weak acid substitution'or depickling, a mixture in'suitable proportions of both of these salts may be employed. It has beendis covered that the use of Glaubers salt gives a greater stretch to the leather whichis desirablein some instances, while common salt gives a tighter skin; and it may be advisable in some cases to combine these saltsto obtain a mediumefiect.

The depickling process in the case of bark tannage is the same as for chrometannag'e.

' It is understood, as has already been'stated, that the percentages; quantities, temperatures and other details of the process just described are stated for example only and may be varied within certain limits without departing from the scope of the invention as set forth in .thefollowing claims. Furthermore, it will be clearly realized tanning or converting the prepared skins into leather. i i

The tanned skins obtained as the result of pursuing the present invention may be subsequently put through various processes such as fat liquoring, crusting and dyeing, but these processes are not part of the present invention and are not set forth in any detail in. the present application;

Having thus described the invention, what is.

claimed as new and desired to be secured by Letters Patent is:

1. In the process of producing leather from skins, the step of treating the pickled skins with a salt of a soluble organic acid; prior to tanning.

2. In, the process of producing leather from skins, the step of, treating the pickled skinswith a salt of an organicjacid together with a quantity of said organic acid itself, prior to tanning.

3. In the process of producing leather from skins, the step of treating the pickled skins with an alkali salt of an organic acid together with a quantity of said organic acid itself, prior to tanning. V

4. In the process of producing leather :from skins, the step of treating the pickled skins with a soluble salt of a soluble fatty organic acid, prior to tanning,

5. In the processor producing leather fr om.

skinswhich have been pickled in a strong acid,

with acetic acid prior to tanning.

the step of replacing the strong acid in the skins 6; In the process of producing skins which havebeen pickled in a strong acid, the step of raising the pH number of the pickled skins to approximately 5 by the replacement of said strong acid byacetic acid. a

'7, In the process of produci the steps of raising the'pH number of the pickled skins to-theneighborhood of 4.8 5.2by. the replacementof said strong acid by a weaker-acid;

ng leather from i v skins whi'chhave been pickled in a strongacid,

leather from 1 and then adding a small quantity of a neutralizing agent in the presence of a solution of a salt of the groupcomprising Glaubers salt and sodium chloride. i

8. In the process of producing leather from pickled skins, the steps of agitating a quantity of such skins in an aqueous solution of Glaubers. salt, sodium acetate and aceticacid, then adding, to the bath an aqueous solution of thorax. and Glaubers salt, and agitating further prior .to tanning.

9. In the process of producingleather from pickled skins, the steps of agitating a quantity of such skins inan aqueous solution of Glaubers salt, sodium acetate and acetic acid, then adding 'to the bath anaq'ueous solution of borax and common salt, and agitating further prior to tan- 104111 the process of producing leather-from pickled skins, the steps of agitating a quantity of such skins in an aqueous solution, of Glaubers salt, sodium acetate and.acetic:acid,qthen adding to the bath an aqueous solution of borax and a mixtureof Glaubers salt and common salt, and agitating" further prior to tanning,

-11..In the process of producingleather from pickled skins, the steps ofagitating a quantity of such skins in an aqueous solution of Glaubers.

salt, sodium acetate and acetic acid for about 30 minutes at about F., then adding to the bath an aqueous solutionjof borax and Glaubers salt, and agitating for a period of about 30 minutes prior to tanning. I

12. In the process of producing leather from pickled skins, the steps of agitating aq'uantity of skins for about 30 minutes at'90 F. in a float of a composition of the following proportions: for 450 pounds of skins, gallons of float containing 100-200 pounds Glaubers salt; about 40.5 pounds I sodium acetate; and about 5.8 pounds acetic acid; then adding to the bath a' solution of about 9.0 pounds bor'ax in about 25 gallons of water with enough Glaubers-salt tofattain a salt concentra tion of about 15%; agitating for 30' minutes at approximately 80 F.; and draining the skins preparatory to tanning.

13. In the process of producingleatherfrom pickled skins, the steps of agitating a quantity of such skins in an aqueous solution of Glaubers salt, sodium acetate andacetic acid such as to raise the pH number of the bath and skins'to about 5.0-5.2, then adding to the bath an aqueous solution of bora'x and Glaubers salt, and agitating prior to tanning.

14. In the process of chrome tanning of skins which have been subjected to pickling in a strong acid, the steps of raising the pH number, of pickled skins to the range of approximately 5.0-6.0 by,

replacement of the strong'acid by acetic acid and maintaining approximately the same range of hydrogen ion concentration throughout the sub sequent chrome tanning process.

15. In the process of chrome tanning 'of'skins which have been subjected to pickling in a strong acid, the steps of replacing the strong acid by a soluble fatty organic acid, adding small quantities of a neutralizing agent, and chrome tanning the skins.

16. In the process of chrome tanning of skins,

V which have been subjected to pickling in a strong acid, the steps of treating the pickled skins with a solution containing the salt of a soluble organic acid, whereby the strong acid is replaced by the weaker organic acid, and tanning the skins with a chrome solution.

17. In the process of chrome tanning of skins, which have been subjected to pickling in a strong acid, the steps of treating the pickled skins with a solution containing the salt of a soluble organic acid-in the'presence of a quantity of said organic acid itself, whereby the strong acid is replaced by the weaker organic acid, adding a small quantity or a neutralizing agent which will not alter the pH number appreciably, and tanning the skins with a chrome solution.

18. In the process of chrome tanning cf skins, which have been subjected to pickling in a strong acid, the steps 01 agitating the pickled skins in a bath containing Glaubers salt, sodium acetate, and acetic acid; adding a solution of borax and Glaubers salt; agitating further; draining the skins; adding asalt solution and agitating while adding successive feeds of basic chromium sulphate until the skins are suitably tanned.

19. In the process of chrome tanning of skins, which have been subjected to pickling in a strong acidfthe steps of agitating the pickled skins in a bath containing common salt, sodium acetate, and acetic acid; adding a solution of borax and common salt; agitating further; draining the skins; adding a salt solution and agitating while adding successive feeds of basic chromium sulphate until the skins are suitably tanned.

20. In the production of leather from skins pickled in the strong acid of the pickle solution, the step comprising replacing the strong acid in said skins with a soluble fatty organic acid.

21. In the production of leather from skins pickled in strong acid, the step comprising reacting the strong acid in said skins with a soluble salt of an organic acid forming an organic acid soluble in water. 7

22. In the production of leather from skins pickled in strong acid, the steps comprising reacting the strong acid in said skins with a soluble salt of an organic acid and partially neutralizing the acid formed.

23. In the production of leather from raw skins pickled in strong acid, thesteps comprising reacting strong acid in said skins with a salt of an organic acid in the presence of a quantity of the organic acid itself. I

24. In the production or leather from skins pickled in strong acid, the steps comprising soaking said skins in a solution containing an alkali salt of an organic acid soluble in water, and, neutralizing the acid in the skins preparatory to converting the skins into leather.

25. In the process of producing leather from skins which have been pickled in a strong acid, the steps of replacing the strong acid in the skins with acetic acid prior to tanning.

26. In the production of leather from raw skins pickled in strong acid, the steps comprising reacting the strong acid in said skins with a salt of acetic acid in the presence of a quantity of acetic acid itself.

GEORGE R. PENSEL. 

